New drain screw + new gasket + old gasket = a little water in new gear oil

[Hezekiah]

1996 Mariner 175 Magnum EFI - Serial OG360900

Got the boat and motor about a month ago. Changed the lower unit gear oil and replaced the drain screw, vent screw and both gaskets around the screws.

Afterwards, got to thinking that I had 2 old screws but only 1 old gasket. I guess I assumed it fell out and I didn't notice it.

3 weeks later (after running the boat about 5 times...never any runs longer than about 5 minutes at a time...maybe 2 hours total on the motor) I check the lower unit oil and notice it is extremely dark with a little discoloration.

I immediately drain the oil and begin investigating.

That's when I find the old seal in the drain plug under the new gasket. So obviously this is where some water got in.

I removed the old gasket and all pieces of it and cleaned off the new gasket real good too. Cleaned the hole, and made sure there were no pieces there - then re-filled the lower unit with oil.

I have not ran it yet - had planned to run it, then drain the oil again and re-fill it with new gear oil, and then depending on what kind of shape the drained oil was in - go from there.


Is this the proper procedure?

Hopefully I caught it before it caused any damage.

Any advice is welcome, thanks.

 

[jerryjerry05]

Any time there is water.
The unit should be pressure tested.

If you put it in the water and run it for a short time, then pull the drain plug.
​If there is a bit of water and discoloration there it could be just the seal?
After the small amount then it goes to the good oil it's probably the gasket..

​Had a Force that the drain plug(not the same style as Mercury) it would weep a bit of water after use.
​Not real bad but enough to keep me changing oil a bit more than I normally would.

But since it's "new to you" a pressure test would be a good thing.

 

[Hezekiah]

My original title and terminology might have been confusing.

It was the old gasket that was left on and the new drain screw and new gasket was installed over it, causing water to get in the lower unit.

I will order a pressure testing kit and do that - but I suspect it will check out well because the old gear oil was fine and the only changes I made were new drain screw, vent screw and new gaskets (around each screw).

Assuming pressure test checks out - I should be okay?

 

[Mohawkmtrs]

You should be fine.

Those crush washers are like a bottle of beer...good for one-time use only.

They're cheap...replace them every time you change oil.

 

[Hezekiah]

You should be fine.

Those crush washers are like a bottle of beer...good for one-time use only.

They're cheap...replace them every time you change oil.

Okay, thanks. And will replace them every time...and NOT FORGET to remove the old ones.

I am hoping I caught it in time without causing any damage. The gear oil I drained out still seemed to have it's lubricating properties...it was not sludge or anything yet...

Finger crossed.